The entire disclosure of Japanese Patent Application No. 2007-184247, filed Jul. 13, 2007, is expressly incorporated herein by reference.
1.Technical Field
The present invention relates to a liquid ejecting apparatus. More specifically, the present invention relates to a liquid ejecting apparatus which includes a movable cap which is capable of capping the liquid ejecting heads of the liquid ejecting apparatus.
2. Related Art
On example of a liquid ejecting apparatus currently known in the art which includes cap units is the line printer disclosed in the published Japanese Patent Application Nos. JP-A-2007-69448 (see paragraphs [0050], [0051], and FIGS. 7 and 8) and JP-A-2005-67127 (see paragraph [0055], and FIGS. 2B and 12). In each description, the line printer includes a plurality of transport belts capable of transporting sheets of paper through the printer, liquid ejecting heads that are arranged in zigzag positions which correspond to the gaps between the plurality of transport belts, and cap units or head recovery units that are provided below the recording heads at locations that correspond to the gaps between the transport belts. Each of the cap units comprises a cap with a surface that corresponds to the nozzles of the recording heads. When the printer is not performing a printing operation, the cap comes into contact with the surface of the recording head in order to cap the nozzles of the recording head, in order to prevent an increase in the viscosity of ink in the nozzles and the ink from drying.
The cap unit also includes a suction pump which acts as a suction unit. The suction pump is driven when the caps are in a capping state in order to create a negative internal pressure in the caps, which forcibly sucks and discharges any high-viscosity ink or bubbles that may have formed in the nozzles. In this way, the nozzles are cleaned. Because the recording heads are at fixed locations within the line printer, the caps are disposed at positions which face the recording heads. During a printing operation wherein sheets are transported through the printer, the caps are moved downward into a retreated position so as not to hinder the transportation of the sheet.
When a printing operation is not being performed and the printer is in print standby mode, no paper is being transported through the printer, so the caps are moved upward to a capping position where the caps come into contact with the nozzle surface of the recording heads.
However, in the line head printer described above, the sheet is transported between the recording heads and the caps during the printing operation. Unfortunately, however, as the paper is transported through the printer, powder is likely to be generated due to the friction between the sheet of paper and the rollers or belts of the transporting system. Tis powder may adhere to the caps.
Japanese Patent Application No. JP-2005-116330 discloses a serial printer which includes cap covers that cover caps when the caps are moved away from the recording heads. In this printer, since the caps are arranged away from the printing area, it is possible to prevent the paper powder from adhering to the caps.
However, in the line printer described above, the caps are always arranged below the recording heads, regardless of whether or not the printer is performing a printing operation, meaning that the paper powder generated from the sheet may adhere to the caps. This creates a number of difficulties. For instance, when the paper powder is adheres to the sealing members of the caps, gaps may form between the nozzle surfaces of the recording heads and the sealing members of the caps, which may cause capping errors and a less effective seal between the caps and the recording head. In addition, it is difficult to remove the paper powder once it is adhered to the sealing members of the caps.
The capping errors lower the sealing performance of the caps, and cause an increase in the viscosity of ink in the capped nozzles, resulting in clogged nozzles. The low sealing performance of the caps may accelerate the drying of ink remaining in the caps and may also clog the ink discharge tube connected to the caps. In addition, the ink in the caps is used to maintain the humidity in the caps during the capping operation, which makes it possible to prevent an increase in the viscosity of ink in the nozzles. However, when the ink remaining in the caps is dried due to the capping error, the humidity is lowered, and the nozzles are more likely to be clogged.